It can can certainly get better as the kids get older, take date nights and leave the kids at home for an afternoon (once old enough and sensible enough).
However, it can also get worse with time if there is something more deep rooted.
Sounds from your initial post that you are expecting a spark to be there without putting effort in to reignite it (could be unfair there?).
Relationships are about putting in enough and getting back enough, its not a magic formula, but if both parties put themselves into the relationship then the effects magnify.
I think its natural for many (all?) long term relationships to have wobbly months or years, you have to get through them and recreate the good stuff.
Good luck.